<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    div{width: 100px;height: 100px;border: 1px solid red}
    div:hover{
        /*margin: 20px 0 0 20px;*/
        position: relative;/*相对定位*/
        /*通过left/right/top/bottom相对于元素初始位置做偏移*/
        top: 20px;
        left: 20px;
    }
  </style>
</head>
<body>
<div>div1</div>
<div>div2</div>
<div>div3</div>
</body>
</html>